The photosensitive members described herein can be used as photosensitive members, photoreceptors or photoconductors useful in electrostatographic, including printers, copiers, other reproductive devices, and digital apparatuses. In specific embodiments, the photosensitive member comprises an elastomeric charge transport layer, having a specific glass transition temperature, and a protective overcoat layer.
Electrophotographic imaging members, including photoreceptors or photoconductors, typically include a photoconductive layer formed on an electrically conductive substrate or formed on layers between the substrate and photoconductive layer. The photoconductive layer is an insulator in the dark, so that during machine imaging processes, electric charges are retained on its surface. Upon exposure to light, the charge is dissipated, and an image can be formed thereon, developed using a developer material, transferred to a copy substrate, and fused thereto to form a copy or print. Electrophotographic imaging members are typically in rigid drum configuration and flexible belt form. Flexible imaging member belts may either be seamed or seamless belts. However, for reasons of simplicity, the disclosures hereinafter will focus only on electrophotographic imaging members in flexible belt form.
In typical negatively-charged electrophotographic imaging members, the top outermost exposed photoconductive layer is a charge transport layer. Therefore, the charge transport layer not only is repeatedly subjected to various machine subsystems mechanical interactions, it is also constantly exposed to corona effluents (emitted from charging device), and other volatile chemical (VOC) species/contaminants. Mechanical interactions against imaging member have caused charge transport layer wear, while corona effluent and chemical contaminants exposure gives rise to charge transport layer material degradation and lateral charge migration (LCM) problems. Charge transport layer material degradation and wear promote premature onset of mechanical failure and LCM impacts copy image quality print out.
Many advanced imaging systems are based on the use of a flexible imaging member belt mounted over and around a belt support module design using small diameter belt rollers to provide ease of paper stripping. The use of small diameters in belt module support rollers for the benefit of easy paper copy stripping is seen to be negated by the large charge transport layer bending strain induced during dynamic fatigue belt bending and/or flexing over each belt module support roller under normal machine functioning conditions. Imaging member bending strain leads to the development of charge transport layer cracking, which then manifests into copy print-out defects and limits the imaging member belt useful life. Moreover, exhibition of imaging member belt charge transport layer cracking has frequently been found to occur at those belt segments parked over the support rollers during prolong machine idling or overnight and weekend shut off periods brought on as a result of exposure to residual corona effluents and airborne chemical contaminants. The early onset of charge transport layer cracking is a serious belt material failure issue that impacts copy print out quality. This results in cutting short the functional performance of the imaging member belt prior to reaching its intended service belt life goal.
For typical negatively-charged imaging member belts, such as flexible photoreceptor belt designs, there are multiple layers comprised of a supporting substrate, a conductive ground plane, a charge blocking layer, an optional adhesive layer, a charge generating layer, and a outermost exposed charge transport layer. Flexible photoreceptor belts may also require an anti-curl back coating applied to the back side of the support substrate to render belt flatness.
Therefore, it is desired to provide an improved photoreceptor belt having a mechanically robust function, wherein the charge transport layer is less susceptible to cracking induced by fatigue bending, and is less susceptible to material failures due to exposure to contaminants from airborne chemical species and corona effluents.